/*
 * Copyright © 2004 Texas Instruments, Jian Zhang <jzhang@ti.com>
 * Copyright © 2004 Micron Technology Inc.
 * Copyright © 2004 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#define CONFIG_MTD_NAND_OMAP_HWECC

#include <linux/platform_device.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <linux/jiffies.h>
#include <linux/sched.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/partitions.h>
#include <linux/io.h>
#include <linux/slab.h>

#include <plat/dma.h>
#include <plat/gpmc.h>
#include <plat/nand.h>

#define	DRIVER_NAME	"omap2-nand"

#define NAND_Ecc_P1e		(1 << 0)
#define NAND_Ecc_P2e		(1 << 1)
#define NAND_Ecc_P4e		(1 << 2)
#define NAND_Ecc_P8e		(1 << 3)
#define NAND_Ecc_P16e		(1 << 4)
#define NAND_Ecc_P32e		(1 << 5)
#define NAND_Ecc_P64e		(1 << 6)
#define NAND_Ecc_P128e		(1 << 7)
#define NAND_Ecc_P256e		(1 << 8)
#define NAND_Ecc_P512e		(1 << 9)
#define NAND_Ecc_P1024e		(1 << 10)
#define NAND_Ecc_P2048e		(1 << 11)

#define NAND_Ecc_P1o		(1 << 16)
#define NAND_Ecc_P2o		(1 << 17)
#define NAND_Ecc_P4o		(1 << 18)
#define NAND_Ecc_P8o		(1 << 19)
#define NAND_Ecc_P16o		(1 << 20)
#define NAND_Ecc_P32o		(1 << 21)
#define NAND_Ecc_P64o		(1 << 22)
#define NAND_Ecc_P128o		(1 << 23)
#define NAND_Ecc_P256o		(1 << 24)
#define NAND_Ecc_P512o		(1 << 25)
#define NAND_Ecc_P1024o		(1 << 26)
#define NAND_Ecc_P2048o		(1 << 27)

#define TF(value)	(value ? 1 : 0)

#define P2048e(a)	(TF(a & NAND_Ecc_P2048e)	<< 0)
#define P2048o(a)	(TF(a & NAND_Ecc_P2048o)	<< 1)
#define P1e(a)		(TF(a & NAND_Ecc_P1e)		<< 2)
#define P1o(a)		(TF(a & NAND_Ecc_P1o)		<< 3)
#define P2e(a)		(TF(a & NAND_Ecc_P2e)		<< 4)
#define P2o(a)		(TF(a & NAND_Ecc_P2o)		<< 5)
#define P4e(a)		(TF(a & NAND_Ecc_P4e)		<< 6)
#define P4o(a)		(TF(a & NAND_Ecc_P4o)		<< 7)

#define P8e(a)		(TF(a & NAND_Ecc_P8e)		<< 0)
#define P8o(a)		(TF(a & NAND_Ecc_P8o)		<< 1)
#define P16e(a)		(TF(a & NAND_Ecc_P16e)		<< 2)
#define P16o(a)		(TF(a & NAND_Ecc_P16o)		<< 3)
#define P32e(a)		(TF(a & NAND_Ecc_P32e)		<< 4)
#define P32o(a)		(TF(a & NAND_Ecc_P32o)		<< 5)
#define P64e(a)		(TF(a & NAND_Ecc_P64e)		<< 6)
#define P64o(a)		(TF(a & NAND_Ecc_P64o)		<< 7)

#define P128e(a)	(TF(a & NAND_Ecc_P128e)		<< 0)
#define P128o(a)	(TF(a & NAND_Ecc_P128o)		<< 1)
#define P256e(a)	(TF(a & NAND_Ecc_P256e)		<< 2)
#define P256o(a)	(TF(a & NAND_Ecc_P256o)		<< 3)
#define P512e(a)	(TF(a & NAND_Ecc_P512e)		<< 4)
#define P512o(a)	(TF(a & NAND_Ecc_P512o)		<< 5)
#define P1024e(a)	(TF(a & NAND_Ecc_P1024e)	<< 6)
#define P1024o(a)	(TF(a & NAND_Ecc_P1024o)	<< 7)

#define P8e_s(a)	(TF(a & NAND_Ecc_P8e)		<< 0)
#define P8o_s(a)	(TF(a & NAND_Ecc_P8o)		<< 1)
#define P16e_s(a)	(TF(a & NAND_Ecc_P16e)		<< 2)
#define P16o_s(a)	(TF(a & NAND_Ecc_P16o)		<< 3)
#define P1e_s(a)	(TF(a & NAND_Ecc_P1e)		<< 4)
#define P1o_s(a)	(TF(a & NAND_Ecc_P1o)		<< 5)
#define P2e_s(a)	(TF(a & NAND_Ecc_P2e)		<< 6)
#define P2o_s(a)	(TF(a & NAND_Ecc_P2o)		<< 7)

#define P4e_s(a)	(TF(a & NAND_Ecc_P4e)		<< 0)
#define P4o_s(a)	(TF(a & NAND_Ecc_P4o)		<< 1)

#ifdef CONFIG_MTD_PARTITIONS
static const char *part_probes[] = { "cmdlinepart", NULL };
#endif

#ifdef CONFIG_MTD_NAND_OMAP_PREFETCH
static int use_prefetch = 1;

/* "modprobe ... use_prefetch=0" etc */
module_param(use_prefetch, bool, 0);
MODULE_PARM_DESC(use_prefetch, "enable/disable use of PREFETCH");

#ifdef CONFIG_MTD_NAND_OMAP_PREFETCH_DMA
static int use_dma = 1;

/* "modprobe ... use_dma=0" etc */
module_param(use_dma, bool, 0);
MODULE_PARM_DESC(use_dma, "enable/disable use of DMA");
#else
const int use_dma;
#endif
#else
const int use_prefetch;
const int use_dma;
#endif

struct omap_nand_info {
	struct nand_hw_control		controller;
	struct omap_nand_platform_data	*pdata;
	struct mtd_info			mtd;
	struct mtd_partition		*parts;
	struct nand_chip		nand;
	struct platform_device		*pdev;

	int				gpmc_cs;
	unsigned long			phys_base;
	struct completion		comp;
	int				dma_ch;
};

/**
 * omap_hwcontrol - hardware specific access to control-lines
 * @mtd: MTD device structure
 * @cmd: command to device
 * @ctrl:
 * NAND_NCE: bit 0 -> don't care
 * NAND_CLE: bit 1 -> Command Latch
 * NAND_ALE: bit 2 -> Address Latch
 *
 * NOTE: boards may use different bits for these!!
 */
static void omap_hwcontrol(struct mtd_info *mtd, int cmd, unsigned int ctrl)
{
	struct omap_nand_info *info = container_of(mtd,
					struct omap_nand_info, mtd);

	if (cmd != NAND_CMD_NONE) {
		if (ctrl & NAND_CLE)
			gpmc_nand_write(info->gpmc_cs, GPMC_NAND_COMMAND, cmd);

		else if (ctrl & NAND_ALE)
			gpmc_nand_write(info->gpmc_cs, GPMC_NAND_ADDRESS, cmd);

		else /* NAND_NCE */
			gpmc_nand_write(info->gpmc_cs, GPMC_NAND_DATA, cmd);
	}
}

/**
 * omap_read_buf8 - read data from NAND controller into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf8(struct mtd_info *mtd, u_char *buf, int len)
{
	struct nand_chip *nand = mtd->priv;

	ioread8_rep(nand->IO_ADDR_R, buf, len);
}

/**
 * omap_write_buf8 - write buffer to NAND controller
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf8(struct mtd_info *mtd, const u_char *buf, int len)
{
	struct omap_nand_info *info = container_of(mtd,
						struct omap_nand_info, mtd);
	u_char *p = (u_char *)buf;
	u32	status = 0;

	while (len--) {
		iowrite8(*p++, info->nand.IO_ADDR_W);
		/* wait until buffer is available for write */
		do {
			status = gpmc_read_status(GPMC_STATUS_BUFFER);
		} while (!status);
	}
}

/**
 * omap_read_buf16 - read data from NAND controller into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf16(struct mtd_info *mtd, u_char *buf, int len)
{
	struct nand_chip *nand = mtd->priv;

	ioread16_rep(nand->IO_ADDR_R, buf, len / 2);
}

/**
 * omap_write_buf16 - write buffer to NAND controller
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf16(struct mtd_info *mtd, const u_char * buf, int len)
{
	struct omap_nand_info *info = container_of(mtd,
						struct omap_nand_info, mtd);
	u16 *p = (u16 *) buf;
	u32	status = 0;
	/* FIXME try bursts of writesw() or DMA ... */
	len >>= 1;

	while (len--) {
		iowrite16(*p++, info->nand.IO_ADDR_W);
		/* wait until buffer is available for write */
		do {
			status = gpmc_read_status(GPMC_STATUS_BUFFER);
		} while (!status);
	}
}

/**
 * omap_read_buf_pref - read data from NAND controller into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf_pref(struct mtd_info *mtd, u_char *buf, int len)
{
	struct omap_nand_info *info = container_of(mtd,
						struct omap_nand_info, mtd);
	uint32_t r_count = 0;
	int ret = 0;
	u32 *p = (u32 *)buf;

	/* take care of subpage reads */
	if (len % 4) {
		if (info->nand.options & NAND_BUSWIDTH_16)
			omap_read_buf16(mtd, buf, len % 4);
		else
			omap_read_buf8(mtd, buf, len % 4);
		p = (u32 *) (buf + len % 4);
		len -= len % 4;
	}

	/* configure and start prefetch transfer */
	ret = gpmc_prefetch_enable(info->gpmc_cs, 0x0, len, 0x0);
	if (ret) {
		/* PFPW engine is busy, use cpu copy method */
		if (info->nand.options & NAND_BUSWIDTH_16)
			omap_read_buf16(mtd, buf, len);
		else
			omap_read_buf8(mtd, buf, len);
	} else {
		p = (u32 *) buf;
		do {
			r_count = gpmc_read_status(GPMC_PREFETCH_FIFO_CNT);
			r_count = r_count >> 2;
			ioread32_rep(info->nand.IO_ADDR_R, p, r_count);
			p += r_count;
			len -= r_count << 2;
		} while (len);
		/* disable and stop the PFPW engine */
		gpmc_prefetch_reset(info->gpmc_cs);
	}
}

/**
 * omap_write_buf_pref - write buffer to NAND controller
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf_pref(struct mtd_info *mtd,
					const u_char *buf, int len)
{
	struct omap_nand_info *info = container_of(mtd,
						struct omap_nand_info, mtd);
	uint32_t pref_count = 0, w_count = 0;
	int i = 0, ret = 0;
	u16 *p;

	/* take care of subpage writes */
	if (len % 2 != 0) {
		writeb(*buf, info->nand.IO_ADDR_W);
		p = (u16 *)(buf + 1);
		len--;
	}

	/*  configure and start prefetch transfer */
	ret = gpmc_prefetch_enable(info->gpmc_cs, 0x0, len, 0x1);
	if (ret) {
		/* PFPW engine is busy, use cpu copy method */
		if (info->nand.options & NAND_BUSWIDTH_16)
			omap_write_buf16(mtd, buf, len);
		else
			omap_write_buf8(mtd, buf, len);
	} else {
		p = (u16 *) buf;
		while (len) {
			w_count = gpmc_read_status(GPMC_PREFETCH_FIFO_CNT);
			w_count = w_count >> 1;
			for (i = 0; (i < w_count) && len; i++, len -= 2)
				iowrite16(*p++, info->nand.IO_ADDR_W);
		}
		/* wait for data to flushed-out before reset the prefetch */
		do {
			pref_count = gpmc_read_status(GPMC_PREFETCH_COUNT);
		} while (pref_count);
		/* disable and stop the PFPW engine */
		gpmc_prefetch_reset(info->gpmc_cs);
	}
}

#ifdef CONFIG_MTD_NAND_OMAP_PREFETCH_DMA
/*
 * omap_nand_dma_cb: callback on the completion of dma transfer
 * @lch: logical channel
 * @ch_satuts: channel status
 * @data: pointer to completion data structure
 */
static void omap_nand_dma_cb(int lch, u16 ch_status, void *data)
{
	complete((struct completion *) data);
}

/*
 * omap_nand_dma_transfer: configer and start dma transfer
 * @mtd: MTD device structure
 * @addr: virtual address in RAM of source/destination
 * @len: number of data bytes to be transferred
 * @is_write: flag for read/write operation
 */
static inline int omap_nand_dma_transfer(struct mtd_info *mtd, void *addr,
					unsigned int len, int is_write)
{
	struct omap_nand_info *info = container_of(mtd,
					struct omap_nand_info, mtd);
	uint32_t prefetch_status = 0;
	enum dma_data_direction dir = is_write ? DMA_TO_DEVICE :
							DMA_FROM_DEVICE;
	dma_addr_t dma_addr;
	int ret;

	/* The fifo depth is 64 bytes. We have a sync at each frame and frame
	 * length is 64 bytes.
	 */
	int buf_len = len >> 6;

	if (addr >= high_memory) {
		struct page *p1;

		if (((size_t)addr & PAGE_MASK) !=
			((size_t)(addr + len - 1) & PAGE_MASK))
			goto out_copy;
		p1 = vmalloc_to_page(addr);
		if (!p1)
			goto out_copy;
		addr = page_address(p1) + ((size_t)addr & ~PAGE_MASK);
	}

	dma_addr = dma_map_single(&info->pdev->dev, addr, len, dir);
	if (dma_mapping_error(&info->pdev->dev, dma_addr)) {
		dev_err(&info->pdev->dev,
			"Couldn't DMA map a %d byte buffer\n", len);
		goto out_copy;
	}

	if (is_write) {
	    omap_set_dma_dest_params(info->dma_ch, 0, OMAP_DMA_AMODE_CONSTANT,
						info->phys_base, 0, 0);
	    omap_set_dma_src_params(info->dma_ch, 0, OMAP_DMA_AMODE_POST_INC,
							dma_addr, 0, 0);
	    omap_set_dma_transfer_params(info->dma_ch, OMAP_DMA_DATA_TYPE_S32,
					0x10, buf_len, OMAP_DMA_SYNC_FRAME,
					OMAP24XX_DMA_GPMC, OMAP_DMA_DST_SYNC);
	} else {
	    omap_set_dma_src_params(info->dma_ch, 0, OMAP_DMA_AMODE_CONSTANT,
						info->phys_base, 0, 0);
	    omap_set_dma_dest_params(info->dma_ch, 0, OMAP_DMA_AMODE_POST_INC,
							dma_addr, 0, 0);
	    omap_set_dma_transfer_params(info->dma_ch, OMAP_DMA_DATA_TYPE_S32,
					0x10, buf_len, OMAP_DMA_SYNC_FRAME,
					OMAP24XX_DMA_GPMC, OMAP_DMA_SRC_SYNC);
	}
	/*  configure and start prefetch transfer */
	ret = gpmc_prefetch_enable(info->gpmc_cs, 0x1, len, is_write);
	if (ret)
		/* PFPW engine is busy, use cpu copy methode */
		goto out_copy;

	init_completion(&info->comp);

	omap_start_dma(info->dma_ch);

	/* setup and start DMA using dma_addr */
	wait_for_completion(&info->comp);

	do {
		prefetch_status = gpmc_read_status(GPMC_PREFETCH_COUNT);
	} while (prefetch_status);
	/* disable and stop the PFPW engine */
	gpmc_prefetch_reset();

	dma_unmap_single(&info->pdev->dev, dma_addr, len, dir);
	return 0;

out_copy:
	if (info->nand.options & NAND_BUSWIDTH_16)
		is_write == 0 ? omap_read_buf16(mtd, (u_char *) addr, len)
			: omap_write_buf16(mtd, (u_char *) addr, len);
	else
		is_write == 0 ? omap_read_buf8(mtd, (u_char *) addr, len)
			: omap_write_buf8(mtd, (u_char *) addr, len);
	return 0;
}
#else
static void omap_nand_dma_cb(int lch, u16 ch_status, void *data) {}
static inline int omap_nand_dma_transfer(struct mtd_info *mtd, void *addr,
					unsigned int len, int is_write)
{
	return 0;
}
#endif

/**
 * omap_read_buf_dma_pref - read data from NAND controller into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf_dma_pref(struct mtd_info *mtd, u_char *buf, int len)
{
	if (len <= mtd->oobsize)
		omap_read_buf_pref(mtd, buf, len);
	else
		/* start transfer in DMA mode */
		omap_nand_dma_transfer(mtd, buf, len, 0x0);
}

/**
 * omap_write_buf_dma_pref - write buffer to NAND controller
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf_dma_pref(struct mtd_info *mtd,
					const u_char *buf, int len)
{
	if (len <= mtd->oobsize)
		omap_write_buf_pref(mtd, buf, len);
	else
		/* start transfer in DMA mode */
		omap_nand_dma_transfer(mtd, (u_char *) buf, len, 0x1);
}

/**
 * omap_verify_buf - Verify chip data against buffer
 * @mtd: MTD device structure
 * @buf: buffer containing the data to compare
 * @len: number of bytes to compare
 */
static int omap_verify_buf(struct mtd_info *mtd, const u_char * buf, int len)
{
	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
							mtd);
	u16 *p = (u16 *) buf;

	len >>= 1;
	while (len--) {
		if (*p++ != cpu_to_le16(readw(info->nand.IO_ADDR_R)))
			return -EFAULT;
	}

	return 0;
}

#ifdef CONFIG_MTD_NAND_OMAP_HWECC

/**
 * gen_true_ecc - This function will generate true ECC value
 * @ecc_buf: buffer to store ecc code
 *
 * This generated true ECC value can be used when correcting
 * data read from NAND flash memory core
 */
static void gen_true_ecc(u8 *ecc_buf)
{
	u32 tmp = ecc_buf[0] | (ecc_buf[1] << 16) |
		((ecc_buf[2] & 0xF0) << 20) | ((ecc_buf[2] & 0x0F) << 8);

	ecc_buf[0] = ~(P64o(tmp) | P64e(tmp) | P32o(tmp) | P32e(tmp) |
			P16o(tmp) | P16e(tmp) | P8o(tmp) | P8e(tmp));
	ecc_buf[1] = ~(P1024o(tmp) | P1024e(tmp) | P512o(tmp) | P512e(tmp) |
			P256o(tmp) | P256e(tmp) | P128o(tmp) | P128e(tmp));
	ecc_buf[2] = ~(P4o(tmp) | P4e(tmp) | P2o(tmp) | P2e(tmp) | P1o(tmp) |
			P1e(tmp) | P2048o(tmp) | P2048e(tmp));
}

/**
 * omap_compare_ecc - Detect (2 bits) and correct (1 bit) error in data
 * @ecc_data1:  ecc code from nand spare area
 * @ecc_data2:  ecc code from hardware register obtained from hardware ecc
 * @page_data:  page data
 *
 * This function compares two ECC's and indicates if there is an error.
 * If the error can be corrected it will be corrected to the buffer.
 */
static int omap_compare_ecc(u8 *ecc_data1,	/* read from NAND memory */
			    u8 *ecc_data2,	/* read from register */
			    u8 *page_data)
{
	uint	i;
	u8	tmp0_bit[8], tmp1_bit[8], tmp2_bit[8];
	u8	comp0_bit[8], comp1_bit[8], comp2_bit[8];
	u8	ecc_bit[24];
	u8	ecc_sum = 0;
	u8	find_bit = 0;
	uint	find_byte = 0;
	int	isEccFF;

	isEccFF = ((*(u32 *)ecc_data1 & 0xFFFFFF) == 0xFFFFFF);

	gen_true_ecc(ecc_data1);
	gen_true_ecc(ecc_data2);

	for (i = 0; i <= 2; i++) {
		*(ecc_data1 + i) = ~(*(ecc_data1 + i));
		*(ecc_data2 + i) = ~(*(ecc_data2 + i));
	}

	for (i = 0; i < 8; i++) {
		tmp0_bit[i]     = *ecc_data1 % 2;
		*ecc_data1	= *ecc_data1 / 2;
	}

	for (i = 0; i < 8; i++) {
		tmp1_bit[i]	 = *(ecc_data1 + 1) % 2;
		*(ecc_data1 + 1) = *(ecc_data1 + 1) / 2;
	}

	for (i = 0; i < 8; i++) {
		tmp2_bit[i]	 = *(ecc_data1 + 2) % 2;
		*(ecc_data1 + 2) = *(ecc_data1 + 2) / 2;
	}

	for (i = 0; i < 8; i++) {
		comp0_bit[i]     = *ecc_data2 % 2;
		*ecc_data2       = *ecc_data2 / 2;
	}

	for (i = 0; i < 8; i++) {
		comp1_bit[i]     = *(ecc_data2 + 1) % 2;
		*(ecc_data2 + 1) = *(ecc_data2 + 1) / 2;
	}

	for (i = 0; i < 8; i++) {
		comp2_bit[i]     = *(ecc_data2 + 2) % 2;
		*(ecc_data2 + 2) = *(ecc_data2 + 2) / 2;
	}

	for (i = 0; i < 6; i++)
		ecc_bit[i] = tmp2_bit[i + 2] ^ comp2_bit[i + 2];

	for (i = 0; i < 8; i++)
		ecc_bit[i + 6] = tmp0_bit[i] ^ comp0_bit[i];

	for (i = 0; i < 8; i++)
		ecc_bit[i + 14] = tmp1_bit[i] ^ comp1_bit[i];

	ecc_bit[22] = tmp2_bit[0] ^ comp2_bit[0];
	ecc_bit[23] = tmp2_bit[1] ^ comp2_bit[1];

	for (i = 0; i < 24; i++)
		ecc_sum += ecc_bit[i];

	switch (ecc_sum) {
	case 0:
		/* Not reached because this function is not called if
		 *  ECC values are equal
		 */
		return 0;

	case 1:
		/* Uncorrectable error */
		DEBUG(MTD_DEBUG_LEVEL0, "ECC UNCORRECTED_ERROR 1\n");
		return -1;

	case 11:
		/* UN-Correctable error */
		DEBUG(MTD_DEBUG_LEVEL0, "ECC UNCORRECTED_ERROR B\n");
		return -1;

	case 12:
		/* Correctable error */
		find_byte = (ecc_bit[23] << 8) +
			    (ecc_bit[21] << 7) +
			    (ecc_bit[19] << 6) +
			    (ecc_bit[17] << 5) +
			    (ecc_bit[15] << 4) +
			    (ecc_bit[13] << 3) +
			    (ecc_bit[11] << 2) +
			    (ecc_bit[9]  << 1) +
			    ecc_bit[7];

		find_bit = (ecc_bit[5] << 2) + (ecc_bit[3] << 1) + ecc_bit[1];

		DEBUG(MTD_DEBUG_LEVEL0, "Correcting single bit ECC error at "
				"offset: %d, bit: %d\n", find_byte, find_bit);

		page_data[find_byte] ^= (1 << find_bit);

		return 0;
	default:
		if (isEccFF) {
			if (ecc_data2[0] == 0 &&
			    ecc_data2[1] == 0 &&
			    ecc_data2[2] == 0)
				return 0;
		}
		DEBUG(MTD_DEBUG_LEVEL0, "UNCORRECTED_ERROR default\n");
		return -1;
	}
}

/**
 * omap_correct_data - Compares the ECC read with HW generated ECC
 * @mtd: MTD device structure
 * @dat: page data
 * @read_ecc: ecc read from nand flash
 * @calc_ecc: ecc read from HW ECC registers
 *
 * Compares the ecc read from nand spare area with ECC registers values
 * and if ECC's mismached, it will call 'omap_compare_ecc' for error detection
 * and correction.
 */
static int omap_correct_data(struct mtd_info *mtd, u_char *dat,
				u_char *read_ecc, u_char *calc_ecc)
{
	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
							mtd);
	int blockCnt = 0, i = 0, ret = 0;

	/* Ex NAND_ECC_HW12_2048 */
	if ((info->nand.ecc.mode == NAND_ECC_HW) &&
			(info->nand.ecc.size  == 2048))
		blockCnt = 4;
	else
		blockCnt = 1;

	for (i = 0; i < blockCnt; i++) {
		if (memcmp(read_ecc, calc_ecc, 3) != 0) {
			ret = omap_compare_ecc(read_ecc, calc_ecc, dat);
			if (ret < 0)
				return ret;
		}
		read_ecc += 3;
		calc_ecc += 3;
		dat      += 512;
	}
	return 0;
}

/**
 * omap_calcuate_ecc - Generate non-inverted ECC bytes.
 * @mtd: MTD device structure
 * @dat: The pointer to data on which ecc is computed
 * @ecc_code: The ecc_code buffer
 *
 * Using noninverted ECC can be considered ugly since writing a blank
 * page ie. padding will clear the ECC bytes. This is no problem as long
 * nobody is trying to write data on the seemingly unused page. Reading
 * an erased page will produce an ECC mismatch between generated and read
 * ECC bytes that has to be dealt with separately.
 */
static int omap_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
				u_char *ecc_code)
{
	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
							mtd);
	return gpmc_calculate_ecc(info->gpmc_cs, dat, ecc_code);
}

/**
 * omap_enable_hwecc - This function enables the hardware ecc functionality
 * @mtd: MTD device structure
 * @mode: Read/Write mode
 */
static void omap_enable_hwecc(struct mtd_info *mtd, int mode)
{
	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
							mtd);
	struct nand_chip *chip = mtd->priv;
	unsigned int dev_width = (chip->options & NAND_BUSWIDTH_16) ? 1 : 0;

	gpmc_enable_hwecc(info->gpmc_cs, mode, dev_width, info->nand.ecc.size);
}

#endif

/**
 * omap_wait - wait until the command is done
 * @mtd: MTD device structure
 * @chip: NAND Chip structure
 *
 * Wait function is called during Program and erase operations and
 * the way it is called from MTD layer, we should wait till the NAND
 * chip is ready after the programming/erase operation has completed.
 *
 * Erase can take up to 400ms and program up to 20ms according to
 * general NAND and SmartMedia specs
 */
static int omap_wait(struct mtd_info *mtd, struct nand_chip *chip)
{
	struct nand_chip *this = mtd->priv;
	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
							mtd);
	unsigned long timeo = jiffies;
	int status = NAND_STATUS_FAIL, state = this->state;

	if (state == FL_ERASING)
		timeo += (HZ * 400) / 1000;
	else
		timeo += (HZ * 20) / 1000;

	gpmc_nand_write(info->gpmc_cs,
			GPMC_NAND_COMMAND, (NAND_CMD_STATUS & 0xFF));
	while (time_before(jiffies, timeo)) {
		status = gpmc_nand_read(info->gpmc_cs, GPMC_NAND_DATA);
		if (status & NAND_STATUS_READY)
			break;
		cond_resched();
	}
	return status;
}

/**
 * omap_dev_ready - calls the platform specific dev_ready function
 * @mtd: MTD device structure
 */
static int omap_dev_ready(struct mtd_info *mtd)
{
	unsigned int val = 0;
	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
							mtd);

	val = gpmc_read_status(GPMC_GET_IRQ_STATUS);
	if ((val & 0x100) == 0x100) {
		/* Clear IRQ Interrupt */
		val |= 0x100;
		val &= ~(0x0);
		gpmc_cs_configure(info->gpmc_cs, GPMC_SET_IRQ_STATUS, val);
	} else {
		unsigned int cnt = 0;
		while (cnt++ < 0x1FF) {
			if  ((val & 0x100) == 0x100)
				return 0;
			val = gpmc_read_status(GPMC_GET_IRQ_STATUS);
		}
	}

	return 1;
}

static int __devinit omap_nand_probe(struct platform_device *pdev)
{
	struct omap_nand_info		*info;
	struct omap_nand_platform_data	*pdata;
	int				err;

	pdata = pdev->dev.platform_data;
	if (pdata == NULL) {
		dev_err(&pdev->dev, "platform data missing\n");
		return -ENODEV;
	}

	info = kzalloc(sizeof(struct omap_nand_info), GFP_KERNEL);
	if (!info)
		return -ENOMEM;

	platform_set_drvdata(pdev, info);

	spin_lock_init(&info->controller.lock);
	init_waitqueue_head(&info->controller.wq);

	info->pdev = pdev;

	info->gpmc_cs		= pdata->cs;
	info->phys_base		= pdata->phys_base;

	info->mtd.priv		= &info->nand;
	info->mtd.name		= dev_name(&pdev->dev);
	info->mtd.owner		= THIS_MODULE;

	info->nand.options	|= pdata->devsize ? NAND_BUSWIDTH_16 : 0;
	info->nand.options	|= NAND_SKIP_BBTSCAN;

	/* NAND write protect off */
	gpmc_cs_configure(info->gpmc_cs, GPMC_CONFIG_WP, 0);

	if (!request_mem_region(info->phys_base, NAND_IO_SIZE,
				pdev->dev.driver->name)) {
		err = -EBUSY;
		goto out_free_info;
	}

	info->nand.IO_ADDR_R = ioremap(info->phys_base, NAND_IO_SIZE);
	if (!info->nand.IO_ADDR_R) {
		err = -ENOMEM;
		goto out_release_mem_region;
	}

	info->nand.controller = &info->controller;

	info->nand.IO_ADDR_W = info->nand.IO_ADDR_R;
	info->nand.cmd_ctrl  = omap_hwcontrol;

	/*
	 * If RDY/BSY line is connected to OMAP then use the omap ready
	 * funcrtion and the generic nand_wait function which reads the status
	 * register after monitoring the RDY/BSY line.Otherwise use a standard
	 * chip delay which is slightly more than tR (AC Timing) of the NAND
	 * device and read status register until you get a failure or success
	 */
	if (pdata->dev_ready) {
		info->nand.dev_ready = omap_dev_ready;
		info->nand.chip_delay = 0;
	} else {
		info->nand.waitfunc = omap_wait;
		info->nand.chip_delay = 50;
	}

	if (use_prefetch) {

		info->nand.read_buf   = omap_read_buf_pref;
		info->nand.write_buf  = omap_write_buf_pref;
		if (use_dma) {
			err = omap_request_dma(OMAP24XX_DMA_GPMC, "NAND",
				omap_nand_dma_cb, &info->comp, &info->dma_ch);
			if (err < 0) {
				info->dma_ch = -1;
				printk(KERN_WARNING "DMA request failed."
					" Non-dma data transfer mode\n");
			} else {
				omap_set_dma_dest_burst_mode(info->dma_ch,
						OMAP_DMA_DATA_BURST_16);
				omap_set_dma_src_burst_mode(info->dma_ch,
						OMAP_DMA_DATA_BURST_16);

				info->nand.read_buf   = omap_read_buf_dma_pref;
				info->nand.write_buf  = omap_write_buf_dma_pref;
			}
		}
	} else {
		if (info->nand.options & NAND_BUSWIDTH_16) {
			info->nand.read_buf   = omap_read_buf16;
			info->nand.write_buf  = omap_write_buf16;
		} else {
			info->nand.read_buf   = omap_read_buf8;
			info->nand.write_buf  = omap_write_buf8;
		}
	}
	info->nand.verify_buf = omap_verify_buf;

#ifdef CONFIG_MTD_NAND_OMAP_HWECC
	info->nand.ecc.bytes		= 3;
	info->nand.ecc.size		= 512;
	info->nand.ecc.calculate	= omap_calculate_ecc;
	info->nand.ecc.hwctl		= omap_enable_hwecc;
	info->nand.ecc.correct		= omap_correct_data;
	info->nand.ecc.mode		= NAND_ECC_HW;

#else
	info->nand.ecc.mode = NAND_ECC_SOFT;
#endif

	/* DIP switches on some boards change between 8 and 16 bit
	 * bus widths for flash.  Try the other width if the first try fails.
	 */
	if (nand_scan(&info->mtd, 1)) {
		info->nand.options ^= NAND_BUSWIDTH_16;
		if (nand_scan(&info->mtd, 1)) {
			err = -ENXIO;
			goto out_release_mem_region;
		}
	}

#ifdef CONFIG_MTD_PARTITIONS
	err = parse_mtd_partitions(&info->mtd, part_probes, &info->parts, 0);
	if (err > 0)
		add_mtd_partitions(&info->mtd, info->parts, err);
	else if (pdata->parts)
		add_mtd_partitions(&info->mtd, pdata->parts, pdata->nr_parts);
	else
#endif
		add_mtd_device(&info->mtd);

	platform_set_drvdata(pdev, &info->mtd);

	return 0;

out_release_mem_region:
	release_mem_region(info->phys_base, NAND_IO_SIZE);
out_free_info:
	kfree(info);

	return err;
}

static int omap_nand_remove(struct platform_device *pdev)
{
	struct mtd_info *mtd = platform_get_drvdata(pdev);
	struct omap_nand_info *info = container_of(mtd, struct omap_nand_info,
							mtd);

	platform_set_drvdata(pdev, NULL);
	if (use_dma)
		omap_free_dma(info->dma_ch);

	/* Release NAND device, its internal structures and partitions */
	nand_release(&info->mtd);
	iounmap(info->nand.IO_ADDR_R);
	kfree(&info->mtd);
	return 0;
}

static struct platform_driver omap_nand_driver = {
	.probe		= omap_nand_probe,
	.remove		= omap_nand_remove,
	.driver		= {
		.name	= DRIVER_NAME,
		.owner	= THIS_MODULE,
	},
};

static int __init omap_nand_init(void)
{
	printk(KERN_INFO "%s driver initializing\n", DRIVER_NAME);

	/* This check is required if driver is being
	 * loaded run time as a module
	 */
	if ((1 == use_dma) && (0 == use_prefetch)) {
		printk(KERN_INFO"Wrong parameters: 'use_dma' can not be 1 "
				"without use_prefetch'. Prefetch will not be"
				" used in either mode (mpu or dma)\n");
	}
	return platform_driver_register(&omap_nand_driver);
}

static void __exit omap_nand_exit(void)
{
	platform_driver_unregister(&omap_nand_driver);
}

module_init(omap_nand_init);
module_exit(omap_nand_exit);

MODULE_ALIAS(DRIVER_NAME);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Glue layer for NAND flash on TI OMAP boards");